In a large pot over high heat, bring 4 quarts water and 1 tablespoon salt to boil. Add noodles and cook until tender, about 8 to 10 minutes. Drain well.
Off heat, add butter to pot. Add drained noodles and toss until butter is melted and noodles are evenly coated. Season to taste with salt and pepper (I like 1/4 teaspoon salt and 1/8 teaspoon pepper).
To make the stroganoff:
In a large skillet over medium-high heat, melt 2 tablespoons butter. Add the onion and cook until slightly softened, about 2 minutes. Stir in the mushrooms and cook until they begin to brown, about 2 minutes.
Add the remaining 1 tablespoon of butter, chicken, flour, and paprika. Cook until the chicken begins to brown, about 3 minutes. Add the broth and Worcestershire sauce and bring to a simmer.
Cook until the sauce thickens, about 5 minutes. Stir in the sour cream and cook until the chicken reaches 165 degrees, about 2 minutes longer. Season to taste with salt and pepper (I like 1 teaspoon salt and 1/2 teaspoon pepper).
To serve, place egg noodles in a bowl or on a plate. Top with the chicken mixture and a dollop of sour cream if desired. Garnish with parsley.